Pin flake8<5 as it breaks pytest-flake8, see:

krassowski · krassowski · commit f682bea5957a · 2022-11-19T11:51:04.000Z
tholo/pytest-flake8#87
diff --git a/requirements-dev.txt b/requirements-dev.txt
@@ -1,4 +1,5 @@
 pytest
 pytest-cov
 pytest-flake8
+flake8<5
 mypy
